Something stirs in the Undergrowth

Dedicated to those large boxes at one end of the room
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IslandPink
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#2671 Re: Something stirs in the Undergrowth

Post by IslandPink »

I had a dream last night where I was assembling the system for a test.
The lower midrange horn was pretty compact - only slightly longer than the Yuichi horn !
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JamesD
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#2672 Re: Something stirs in the Undergrowth

Post by JamesD »

Wow!!!

That's really starting to look very impressive - any system that dwarfs a Quasar style baffle is impressive :-)

Really hope this ones sounds as good as you hope it will!

Next step - move into a barn to let it breath :lol:
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IslandPink
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#2673 Re: Something stirs in the Undergrowth

Post by IslandPink »

It is worryingly large though ! Looking at a page of numbers didn't really prepare me for the size of it, with the mouth section done.
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JamesD
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#2674 Re: Something stirs in the Undergrowth

Post by JamesD »

It does seem that, all other things being equal, large (relative to wavelengths reproduced) is the way to go for horns to have a small 'horn' signature... but then they give you back that wonderful unrestricted, dynamic and timbre full sound...

Really admire you for working through all this to get closer to that magical sound that you have in your head!
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IslandPink
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#2675 Re: Something stirs in the Undergrowth

Post by IslandPink »

Send in the reinforcements !
Horn1p9m_mouth_fibre2.JPG
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IslandPink
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#2676 Re: Something stirs in the Undergrowth

Post by IslandPink »

Just finished the second inside surface, so all the fibreboard has at least one layer over it. I'll just do trimming in the next few days and prepare for a soundcheck. My idea that using the spare fibreboard would be a cheap and quick option wasn't very well thought-through. I've already spent £48 on resin, plus about £8 on cheap paintbrushes, so that's getting close to the cost of a full sheet of 18mm birch ply.
The weight of the mouth section will be lower though, so that will be a useful benefit.

Will be glad to be free of the styrene smell in the house though. I went out on the bike earlier, for a late lunch with some friends from Prestatyn. On the way ( to Tremierchion ) there's a 1 in 6 hill. As I was puffing my way up there, I reckon I could smell the styrene smell again, coming out of my lungs, must have been lodged deep in there from Friday and Saturday work.
Last edited by IslandPink on Sun Oct 11, 2020 9:36 pm, edited 2 times in total.
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JamesD
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#2677 Re: Something stirs in the Undergrowth

Post by JamesD »

It was a nice day to be out and about today - a bit blowy but pleasant here in Yorkshire. I don't envy you the styrene smell as that gets everywhere....

What colour are you going to finish the horns? Assuming you like them enough to keep!
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IslandPink
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#2678 Re: Something stirs in the Undergrowth

Post by IslandPink »

JamesD wrote: Sun Oct 11, 2020 8:19 pm What colour are you going to finish the horns?
Horn !
Good question, I could spray over this, even though it's merely a test-bed. perhaps a poll would be good.
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vinylnvalves
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#2679 Re: Something stirs in the Undergrowth

Post by vinylnvalves »

I think you should consider a colour which goes with these..... as one day you never know..( they are collecting dust in attic currently)
15C6119C-03E1-4413-895F-C2E79498B2BC.jpeg
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IslandPink
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#2680 Re: Something stirs in the Undergrowth

Post by IslandPink »

:D I think that's a bit too ostentatious for what I have here at the moment !

Getting this mouth section ready for fitting has been a pain. The trimming of the fibreglass edges on the firbreboard has been messy and painful. I'm just try to finish this off but need either varnish or filler to help consolidate the loose 'fringes' of glass on the edges that fit against the wood section. I was using a dremel with a diamond disc cutter but even that at high speed was pulling the weave off the fibreboard. However I just found a big unopened tin of filler in the scullery so will try that out.
Ps. top tip - do not use a router to trim fibreglass while only wearing short sleeves. That brought up a nice rash !
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#2681 Re: Something stirs in the Undergrowth

Post by IslandPink »

Well , after some more purchasing of bits ( filler, dremel cutting discs etc ) I finally got the mouth section tidy enough to fit to the rest. Yesterday was sound check #2. I must say this thing sort-of dominates the room -
Horn1p9m_complete_test2.JPG
The sound is good but not amazing. It has gained some extension into the bass, with the mouth added. It's a bit hard to evaluate without filtering, as there's a lot more out of band energy ( upper end ) than expected. You have to sort of tune that out when listening and concentrate on things like lower percussion and bass guitars. The mouth section is not rigid enough ( as expected ) it needs another layer of fibreglass, I'll do that inside - plus a brace from top to bottom.
The other thing I need to do its make a back volume for the driver. I think this bigger, longer horn will benefit from this more than ones I've done in the past. This could be a faff, I'm just thinking about how to do it - it'll be cylindrical, using the phase plug surround as the starting point.
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IslandPink
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#2682 Re: Something stirs in the Undergrowth

Post by IslandPink »

Slow progress owing to the usual laziness plus shops being shut for a while. I put another layer of fibreglass on the two inside surfaces. Should help a fair bit, the dull sound of the fibreboard is much reduced when you rap it with knuckles. I also bought some more dowel of the right diameter, to make one or two more stiffening struts for inside.
The bit that's not clearly worked out yet is how to make the back volume around the driver - partly because I'm running out of wood !
The volume will need to be about 12L to start with - I can experiment with reducing this afterwards.
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vinylnvalves
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#2683 Re: Something stirs in the Undergrowth

Post by vinylnvalves »

You can adjust the back chamber volume, with anything incompressible. Plastic bottles partially filed with water can be used to fine tune the back chamber.
Ant
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#2684 Re: Something stirs in the Undergrowth

Post by Ant »

A carboard box and some duck tape will do for testing?
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chris661
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#2685 Re: Something stirs in the Undergrowth

Post by chris661 »

Not sure, Ant. There might be quite a lot of pressure in there.

I'd see about some 8-10" cardboard tube. Cut to different lengths, add gaskets, MDF top and a couple of clamps. Easy to swap in and out.

Chris
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